Eccentric gear

ABSTRACT

An eccentric gear comprises two differently large gear rings (6, 7), of which an outer ring (6) has a certain number of inwardly directed teeth and an inner ring (7) has a smaller number of outwardly directed teeth, of which only a few engage with the outer gear ring, in that the inner gear ring is eccentrically mounted in bearings. The inner gear ring (7) is integrated with a casing part (8) whose geometrical axis of rotation (A) is oblique relative to an axis of symmetry (B) through the center of the outer gear ring (6). During the generation of the inner gear ring, the casing part is submitted to a nutating motion, during which the axis of rotation (A) of the casing part moves as a generatrice along an imaginary cone, around a cone apex (C) that is axially distanced from the gear rings (6, 7). In a region that is equally distanced from the gear rings as the cone apex (C), the casing part is associated with a gear ring (12) that is ready to be led into engagement with a complementary second gear ring on the driven element of an application object in order to, jointly with the latter, form a force transmitting unit situated substantially in a plane (D--D) extending perpendicularly to said axis of symmetry, in which plane the cone apex (C) is located.

TECHNICAL FIELD OF THE INVENTION

This invention relates to an eccentric gear for transmitting a torque orforce from an input or driving, rotatable element to a driven elementcomprising two cooperating gear rings with differing pitch diameters, ofwhich a first, outer gear ring with the largest diameter has a certainnumber of inwardly directed teeth and a second, inner gear ring has asmaller number of outwardly directed teeth of which only a minor number,e.g. one, is in engagement with the outer gear ring, in that the innergear ring is mounted in bearings eccentrically relative to the outerone, the gear change between said driving and driven elements beingdependent upon the total number of teeth in each gear ring.

PRIOR ART

Eccentric gears of the sort generally related to above are previouslyknown in different embodiments. Thus, in SE 9203101-2 an eccentric gearis disclosed that is specially, although not exclusively, suitable forbeing used in industrial or other robots. In this case, the gear isdelivered as an independent unit, which may be inserted between adriving source, for instance an electric motor, and a driven, rotatingelement of the robot or the application object in order to gear down ahigh rotation speed of an output shaft from the driving source to alower speed of an input shaft that forms the driven element of theapplication object. An essential advantage of eccentric gears is thatthey in one single step make possible large gear change relations. Thus,in practice they manage gear changes in the range of 50:1 to 200:1. Incomparison with other types of gears, in particular multiple gears,eccentric gears have a constructional simplicity that has beenconsidered to offer an inexpensive solution to the generally occurringproblem in mechanical engineering to attain large gear changes. However,such previously known eccentric gears that have been series-produced asindependent or separate units for later application with thepurchaser/user have had in common that they have always included both aninput shaft or shaft part centrically mounted in bearings, and an outputshaft or shaft part, likewise centrically mounted in bearings. The innergear ring has then been provided on a ring- or disk-shaped body of asmall axial extension, from which the down-geared rotary motion has beentransferred to the output shaft via carrier mechanisms of a more or lesscomplicated and thereby expensive nature. Each of the two shafts of thegear require not only a bearing, but also the installation spacethereof; often in opposed ends of a more or less voluminous housing inwhich the tooth-carrying, eccentrically movable ring or disk body isbuilt-in. Further, costly and space-demanding connections or couplingsare required not only between the driving source and the input shaft ofthe gear but also between the output shaft of the gear and the drivenrotary element comprised by the application object of thepurchaser/user.

As a further example of an eccentric gear of the sort initially relatedto, the gear disclosed in U.S. Pat. No. 5,030,184 (Rennerfelt) may alsobe mentioned.

OBJECTS AND FEATURES OF THE INVENTION

The present invention aims at removing the above-mentioned shortcomingsof previously known eccentric gears of the sort related to and providinga constructionally extremely simple gear. Thus, a primary object of theinvention is to provide an eccentric gear that not necessarily requiresany output shaft and the bearings belonging thereto and which thereforedoes not require expensive couplings between the gear and theapplication object for its connection to the application object inquestion. Further, it is an object of the invention to provide aneccentric gear that may be connected to an arbitrary application objectin a simple way. Still another object of the invention is to accomplishan eccentric gear which for its function requires very few componentsand which therefore can be produced to a very low cost with the ultimatepurpose of making the use of the gear possible in application areaswhere high costs are unacceptable. In accordance with a particularaspect, the invention aims at providing a gear that is capable ofsetting the driven element of the application object not only in rotarymotion but, also in a simultaneous reciprocate, axial motion. Inaccordance with a further aspect, the invention also aims at providing agear that, despite a simple construction, manages to transform a rotarymotion from the gear into an exclusively reciprocate motion of thedriven element of the application object.

According to the invention, at least the primary object is attained bymeans of providing an eccentric gear comprising two cooperating gearrings with differently sized pitched diameters. A first outer gear ringhaving a large diameter has a certain number of inwardly directly teethand a second inner gear ring has a small number of outwardly directedteeth of which only a minor proportion are in engagement with the outergear ring. The inner gear ring is mounted in bearings eccentricallyrelative to the outer gear ring. The gear change between the driving anddriven elements are dependent upon the total number of teeth in eachgear ring, the eccentric inner gear ring being in the form of separateunit being connectible to an arbitrary application object in which thedriving element is included. The inner gear ring is connected with arotatable, enlongated body whose geometrical axis of rotation is obliquerelative to an imaginary geometrical axis of symmetry through the centerof the outer gear ring in which during the generating motion of theinner gear ring against the outer gear ring is submitted to a rotatingmotion, during which the axis of rotation of the body moves as ageneratrice along the surface of an imaginary cone apex. The body ispositioned within a region substantially equally distanced from the gearring and the cone apex, and is associated with a first engaging meanswhich is adapted for engagement with a complimentary second engagingmeans appurtenant to the driven element of the application object, inorder to jointly with this second means from a force transmitting unitsubstantially situated in a plane that is perpendicular relative to theaxis of symmetry of the plane of the cone apex.

According to a particularly preferred embodiment, the elongated body onwhich the inner eccentrically movable gear rind is formed, has the shapeof a casing or a casing-like part according to a further embodiment thiscasing part can be used for carrying a third gear ring intended to bebrought into engagement with an analogous gear ring that constitutes apart of the driven element of the application object, said drivenelement forming a stationary part in the space that determines theposition of the cone apex around which the casing part moves during itsnutating motion.

FURTHER ELUCIDATION OF PRIOR ART

An eccentric gear mechanism with a tooth-carrying casing part exerting anutating motion during use is previously known per se from WO 93/06999.However, in that case the gear mechanism in included as an integrated,internal component into a cylindrical roll, wherefore a separatearbitrary application object cannot be connected to the gear mechanismat all, and even less so in the simple way that characterizes thepresent invention.

BRIEF DESCRIPTION OF THE APPENDED DRAWINGS

In the drawings:

FIG. 1 is a longitudinal section of an eccentric gear according to theinvention, which at its input side is shown connected to a motor and atits output side is connected to an application object comprising a valvespindle as the driven element,

FIG. 2 is a longitudinal section of only the gear per se,

FIG. 3 is an exploded view of the gear according to FIG. 2,

FIG. 4 is a longitudinal section of a similar, although modifiedembodiment of the gear according to FIG. 1 to 3,

FIG. 5 is a longitudinal section of an alternative embodiment of a gearin which the force transmission between the gear and a driven element ofthe application object is effected via a gear belt,

FIG. 6 is an exploded view showing different details comprised by thegear according to FIG. 5,

FIG. 7 is a longitudinal section corresponding to FIG. 5 showing anembodiment according to which the force transmission to the drivenelement is effected via a simple toothed transmission,

FIG. 8 is a longitudinal section of a gear for force transmission to adriven element via a chain,

FIG. 9 is a longitudinal section of a gear that transforms a rotarymotion of a driving source into an axially reciprocating motion of adriven element, and

FIG. 10 is a partly sectioned side view showing the use of the gear inconnection with a wheel provided with a tire.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In FIG. 1 to 3, reference numeral 1 generally designates an eccentricgear made according to the invention, which gear at its input side isconnected to a driving source in the form of a motor 2, for instance anelectric motor. At its output side, the gear 1 is connected to anapplication object which is schematically shown at reference numeral 3.In the example this object is assumed to be in the form of a valvehousing comprising a valve spindle 4 that is turn- or rotatable for theregulation of the appurtenant valve. In the case where the valve spindle4 comprises a thread, it is also axially movable.

One component in the gear 1 consists of an outer frame-forming ring 5which on its inside has a first gear ring 6 arranged to cooperate in aknown manner with a second gear ring 7 on a rotatable body designated 8.The first outer gear ring 6 has a larger pitch diameter than the gearring 7 and has a certain number of inwardly directed teeth, while theinner gear ring 7 has a smaller number of outwardly directed teeth ofwhich only a minor number, for instance one, is in engagement with theouter gear ring 6, in that the inner gear ring is eccentrically mountedin bearings relative to the outer one. More precisely, the body 8 thatcarries the inner gear ring 7 at its one end is carried by a bearing 9,e.g. a ball bearing, that is arranged outside an eccentric body 10 whichin turn is co-rotatively connected with a shaft 11 pertaining to themotor 2 and which is centrically mounted in the same in bearings. Theeccentric body 10 forms the driving, rotatable input element of theeccentric gear, to which the shaft 11 is connectable. The gear change ofthe gear is dependent upon the total number of teeth in the two gearrings 6, 7. Presume that the number of teeth in the outer gear ring 6amounts to 90 while the number of teeth in the inner gear ring 7 amountsto 89. When the shaft 11 and the eccentric body 10 rotate, then theinner gear ring 7 will generate on the outer gear ring 6 like a planetwheel and thereby turn around its axis of symmetry in the oppositedirection of rotation relative to shaft 11, more specifically by 1 toothpitch since the difference in numbers of teeth is 1. In order to makethe inner gear ring 7 and, thereby, the body 11 rotate a wholerevolution, the shaft 11 has to rotate 89 revolutions. In other terms, agear change or a reduction in the number of revolutions of 89:1 isobtained.

The eccentric gear shown in FIG. 1 to 3 as described so far issubstantially previously known.

According to the invention, the body 8 carrying the inner gear ring 7 iselongated and has in the example according to FIG. 1 to 3 the shape of acasing or casing-like part, which, at its end being distanced from thegear ring 7, has a first means that is ready to be connected or bebrought into engagement with a complementary second means on the valvespindle 4, which constitutes the element driven by the gear. Accordingto the shown example, said first engagement means consists of aninternal third gear ring 12 that is connected or integrated with thefree end portion of the casing part. The complementary engagement meanson the valve spindle 4 consists of a cooperating fourth gear ring 13with outwardly directed teeth, said ring being provided upon adisk-shaped body 14 which is corotatively connected with the valvespindle 4.

The casing part 8 has a geometrical axis of symmetry designated A (seeFIG. 2) which is oblique relative to an imaginary geometrical axis ofsymmetry B through the centre of the outer gear ring 6. During the geargeneration of the inner gear ring 7 against the outer gear ring 6, thecasing part is submitted to a nutating or tilting motion during whichits axis of symmetry A moves like a generatrice along an imaginaryconical surface, more specifically around a cone apex designated C thatis axially distanced by a considerable stretch from the gear rings 6, 7.In the example, each one of the gear rings 6, 7 has a conical basicshape with small ends and large ends. More specifically, the conicity issuch that the small ends of the gear rings point into the samedirection. Specifically in the shown example, they point in a directiontowards the motor 2. It should be observed that the previously mentionedcone apex C is located in a plane designated D--D which extendssubstantially perpendicularly to the axis of symmetry B. The distancebetween this cross plane D--D and the cross plane designated E--E thatextends perpendicularly to the axis of symmetry B and in which the gearrings 6, 7 are located, is substantially as large as the distance of thegear ring 12 to the plane E--E. In other words, the gear ring 12 issubstantially located in the cross plane D--D.

Within the casing part 8 a shoulder 15 is arranged which according tothe example has the form of an intermediate wall. Against this wall isplaced the one end of a pressure spring 16, for instance a helicalpressure spring, whose opposite end is placed against the tooth-carryingdisk-body 14 being carried by the spindle shaft 4. The spring 16 has thepurpose of always keeping the casing part 8 spring-tensioned in adirection towards the motor 2, more specifically for keeping thetooth/teeth of the inner gear ring 7 being engaged with analogous teethon the outer gear ring 6 in a gap-free engagement with the latter. Inthis way, a distinct and silent force transmission is secured betweenthe gear rings.

Necessary lubricating grease for the gear rings 6, 7 is enclosed bymeans of a radial seal 17, preferably a standard seal, which accordingto the example in FIG. 1 to 3 has the shape of a cross-sectionallyV-shaped, elastic ring, e.g. of plastic or rubber. Similarly to the gearring 12, the sealing ring 17 is located in the cross section D--D,

The frame ring 5 has lugs 18, 19, a flange or similar means forfastening the gear 1 to, on one hand, the motor 2 and, on the otherhand, the application object 3. More specifically, the lugs 18 allow ascrew-fastening of the gear to a flange 20 on the motor 2, while thelugs 19 may be screwed to suitable connecting taps or means 21 which inturn are stiffly fastened to the application object 3. In itsscrew-fastened state as shown in FIG. 1, the frame ring is immovable inthe space relative to both the motor 2 and the application object 3.

It should also be pointed out that a cup spring 22 operates between thebearing 9 and an internal shoulder in the casing part 8, with thepurpose of keeping the bearing in place and lightly stressing the sameaxially in order to avoid any looseness.

The Function of the Eccentric Gear According to the Invention

As previously mentioned, the comparatively elongated casing part 8 willperform a nutating or tilting motion when the inner gear ring 7 makes agenerating motion against the outer gear ring 6 in a way similar to aplanet wheel. The size of the angle α that the axis of symmetry A formswith the axis of symmetry B is determined by on one hand the size of theeccentricity of the gear rings 6, 7 and on the other hand the distancebetween the cross planes E--E and D--D. At a small distance betweenthese cross planes, a comparatively large angle α is required for acertain eccentricity. With increasing distance between the cross planes,the angle α may be reduced. In practice, the angle α may lie within therange of 0,1 to 3°, suitably 0,2 to 2° or preferably 0,3 to 1°. Theaxial length of the casing part 8 should amount to at least 50% of thediameter of the gear ring 7 and suitably more in order not tonecessitate too large angles α.

Of course, during the nutating motion of the casing part 8 the innergear ring 12 will obtain a slewing or tilting movement at its right,free end. However, since the gear ring in question is located in thecross plane D--D which is common to the cone apex C, said ring will notobtain any eccentrically or radially directed motion and the deflectionof the axial movement component will be very limited. Therefore, it doesnot present any practical difficulties to absorb these motions in thetooth connection between on one hand the gear ring 12 and on the otherhand the gear ring 13 associated with the valve spindle 4, for instanceby making the teeth with a certain adapted play. It is also feasible tomake the teeth with a certain curvature instead of making themcompletely straight. If the casing part 8 at the end that comprises thegear ring 12 is wholly or partly made of plastic or another plasticmaterial, also a play-free elastic pre-stress may be obtained in thetooth engagement with the gear ring 13.

In FIG. 1 it should particularly be noted that the inner gear ring 12 onthe free end portion of the casing part 8 has a width that is smallerthan the width of the outer gear ring 13 on the disk body 14. Moreover,it should be noted that the inner edge of the gear ring 12 is located ata certain distance from a shoulder surface 23 in the casing part,whereby a gap 24 is created between the shoulder and the gear ring. Bythis shaping, the disk body 14 and the appurtenant gear ring 13 are freeto move axially in both directions without the gear rings 13, 14 losingtheir meshing with each other and without the apex C of the conechanging its spatial position in relation to the fixed frame ring 5 andthe valve housing 3, respectively. Thus, a valve spindle 4 with threadsmay also be connected with the gear without losing the axial mobilitythat is necessary for adjusting the valve in question into differentregulating positions. It should be obvious that the gear attends to agear reduction of the relatively high rotation speed and low torque to areduced rotation speed or deflection of angle of rotation, these beingdependent as a function of the factual gear change, and an increasedtorque of the valve spindle 4.

The advantages of the invention are evident. By the fact that the freelyexposed gear ring 12 is available on the casing part 8, the gear mayeasily and quickly be connected to the valve spindle without thenecessity of any special couplings of the kind that has been previouslyrequired between an output shaft mounted in bearings of the gear and therotation element in question of the application object. Further, thedescribed gear assumes a very simple construction, comprising extremelyfew components, namely substantially only the frame ring 5, the casingpart 8, the bearing 9 and the eccentric body 10, and where appropriate,the spring 16 and the sealing 17. In other terms, the gear can beproduced at a very low cost in comparison with previously knowneccentric gears.

In FIG. 4 a modified embodiment is shown, according to which theV-shaped sealing ring 17 has been replaced by a simple O-ring 25. Alsothis sealing ring is located in the cross plane D--D in which the coneapex C of the casing part 8' is located. In FIG. 3 it is indicated howthe gear ring 12 exerts slewing motions with restricted motiondeflections under the nutating motion of the casing part. Thus, a majorpart of the upper portion of the O-ring is shown situated somewhat tothe right of the cross plane D--D, while the major part of the lowerportion is shown to the left of the same plane. The O-ring 25, which isrelatively stiff in radial direction, simplifies the assemblage of thegear relative to the spindle. The cone apex C should be located on theaxis of symmetry B in order to obtain the best possible contact betweenthe gear rings 6 and 7.

Although the gear ring 12 related with the casing part is shown as aninner ring intended to be connected with an outer gear ring on thedriven element of the application object, also the reversed relation ispossible, i.e., an outer gear ring on the casing part and an inner gearring on the driven element.

Reference is now made to FIG. 5 and 6 that illustrate an alternativeembodiment according to which an element 4' driven by the gear 1 isindicated in the form of a shaft comprised by an arbitrary applicationobject (not shown). The gear comprises a casing part 8", which ismounted in bearings not only by means of a first eccentrically placedbearing 9, but also by means of a centrically placed second bearing 26at the free end of the casing part. This bearing is kept in place bymeans of a holder which is designated 27 in its entirety and whichcomprises an angle-shaped arm 28 being stiffly connected with a framering 5', and a support ring 29 being carried by said arm. The eccentricbody 10', which in this case has a counter-weight 30, has an extension31 whose free end is mounted in bearings in the support ring 29.

According to the embodiment of this example, the casing part 8", has anexternal fifth gear ring 32 which forms the first engaging orforce-transmitting means of the gear. As may be seen in FIG. 5, the gearring 32 engages with a gear belt 33 which in turn engages with a gearbelt disk 34 on the driven shaft 4'.

Similar to the third gear ring 12 of the embodiment according to FIG. 1to 3, the gear ring 32 is located in one and the same cross plane as thecone apex around which the casing part 8" exerts its nutating motion.Also in this case the gear ring 32 makes a slewing or tilting motionwhich, however, has a limited deflection, wherefore the resilient orflexible gear belt 33 manages to absorb the motions in question withoutany problems.

In FIG. 7 an embodiment is shown according to which the stationaryholder 27' for the bearing 26' has the shape of a cover in which thereis an opening 35 for a gear wheel 34' whose teeth are brought intodirect engagement with the gear ring 32'. Thus, in the present case theother engaging means associated with the driven element 4' consists ofthe gear wheel 34' in lieu of the gear belt 33 as according to theembodiment of FIG. 5 and 6.

In FIG. 8 an embodiment is shown according to which the gear in questionis formed for direct connection with a cable or chain transmission. Inthis case an outer, carrying frame ring 5" is fixedly attached to acarrier 36 of a suitable type. At its free outer end the frame 5"carries a bearing 26" on which a chain wheel or sprocket 37 is rotatablymounted, which in turn is co-rotatively connected with a shaft 38 thatconstitutes an extension of a casing part designated 8'". On itsdisk-shaped portion 39, this casing part carries an inner gear ring 7which in a previously described manner cooperates with an outer gearring 6 on the inside of a part-ring 5'" that is detachably connectedwith the frame ring 5". A motor 2 is connected with the gear. The wheel37 has a toothing 40 for engaging with the chain in question. Thistoothing constitutes the first engaging means of the gear.

As according to the previous embodiments, said first engaging means 40is located in the cross plane D--D in which the cone apex C as well asthe bearing 26" are located. In this case the distance between the crossplane D--D and the cross plane for the gear rings 6, 7 is comparativelylarge (larger than the diameter of the gear ring 7), implying that theobliquity angle α° between the previously mentioned shafts A and B maybe comparatively small. Thus, in the embodiment according to FIG. 8, itis feasible that this angle amounts to merely about 0,20-0,309°.

In FIG. 9 an eccentric gear is schematically illustrated, which has thepurpose of transforming a rotary motion of an output shaft of a motor 2into an axial, reciprocating motion of a driven element, e.g. in theform of a swivelling arm 4" to an application object 3' in the form of astationary holder. In this case, a screw or screw-shaped tap 41 isco-rotatively connected with the casing part 8'", the external thread ofsaid screw or screw-shaped tap being in engagement with an internalthread in a through-hole through the holder 3'. When the screw 41 isbrought to rotate by means of the eccentric gear, with a speed ofrotation that is reduced in comparison with the speed of rotation of themotor 2, then the screw 41 will--thanks to the thread engagement--besubmitted to an axial motion which is directed either to the left or tothe right on the drawing, depending on the direction of rotation of thecasing part. In turn, this axial motion of the screw is transformed intoa slowing motion of the arm 4" that is pivotable relative to the holder3' via a joint designated 42. The screw tap 41 may either be fixedlyconnected with the casing part 8'" or be provided with splines. Then thecasing part, and thereby the cone apex C, will be moved axially relativeto the object 3'. This motion is usually small and can be accepted.Alternatively, the threaded tap 41 may constitute the application objectand be provided with splines which engage into corresponding splines inthe casing part 8"" (cf. FIG. 1).

Eventually, in FIG. 10 an embodiment is shown according to which a gear1 according to the invention has the purpose of transmitting a torquefrom a motor 2. e.g. a hydraulic motor, to a wheel 43 with a tire, whichwheel comprises a rubber tyre 43' and a rim part 43". In conformity withthe sprocket 37 according to FIG. 8, the wheel 43 is mounted in abearing 44 which is located in the same cross plane as the cone apex ofa nutating casing part 8'", in a previously described manner. By thelateral resilience of the tire, the tilting motions in question can beaccepted. According to the example in FIG. 10, the rim part 43" formsthe driven element of the application object, which element may beeasily connected via a screw joint 46 with a ring flange 45 that isco-rotatively connected with the casing part 8'".

Feasible Modifications of the Invention

It is evident that the invention is not restricted merely to theembodiments as described and shown in the drawings. Thus, it is forinstance feasible to make the first and second outer and inner gearrings, respectively, of the gear in another way than in the form of gearrings which both have a conical basic shape. Hence, the outer gear ringmay, e.g., be cylindrical at the same time as the inner gear ring isconical. For simple gears with small requirements of accuracy, it iseven feasible to make both gear rings substantially cylinder-shaped.Furthermore, it is feasible to make the teeth of at least one gear ringwith a slight curvature, and it is also feasible to construct the teethso that the contact points between the same extend helically and aredistributed along several consecutive teeth or pairs of teeth. Althougha casing-shaped part is preferred as an elongated, gear ring-carryingbody, the body in question may also be formed in another way. Thus, asindicated in FIG. 8, the elongated body could also consist of adisk-shaped, tooth-carrying part and a central axial tap, being directlyconnected or integrated with the former. It should also be mentionedthat according to the embodiment of FIG. 8, the wheel 37 may be modifiedin different ways in order to make possible the connection of the gearwith other objects than just a chain. The wheel may for instance beformed for being connected with a transmission belt, e.g., a beltencompassed by a patient-lift, it being possible to effect the forcetransmission by a friction engagement between the wheel and the belt.

I claim:
 1. An eccentric gear for transmitting (a) torque or (a) forcefrom a rotatable drive element to a driven element, said driven elementcomprising two cooperating gear rings with differently sized pitchdiameters, of which a first, outer gear ring with the larger diameterhas a certain number of inwardly directed teeth and a second, inner gearring has a smaller number of outwardly directed teeth, of which only aminor proportion is in engagement with the outer gear ring, and in thatthe inner gear ring is mounted in bearings eccentrically relative to theouter gear ring, the gear change between said driving and drivenelements being dependent upon the total number of teeth in each gearring, the eccentric inner gear ring being in the form of a separate unitbeing connectable to an arbitrary application object in which thedriving element is included, such that the inner gear ring is connectedwith a rotatable, elongated body, whose geometrical axis of rotation isoblique relative to an imaginary geometrical axis of symmetry throughthe center of the outer gear ring and which during the generating motionof the inner gear ring against the outer gear ring is submitted to arotating motion, during which the axis of rotation of the body moves asa generatrice along the surface of an imaginary cone the apex of whichis axially distanced from the gear rings, and such that said body issubstantially entirely within a region substantially equally distancedfrom the gear rings as said cone apex, and is associated with a firstengaging means which is adapted for engagement with a complementarysecond engaging means appurtenant to the driven element of theapplication object in order to jointly with this second means form aforce transmitting unit substantially situated in a plane that isperpendicular relative to said axis of symmetry, in which plane saidcone apex is located.
 2. An eccentric gear according to claim 1, whereinthe first engaging means has the form of a third gear ring which isarranged at the end portion of the elongated body being distanced fromthe inner gear ring and intended to be brought into engagement with ananalogous, fourth gear ring that makes part of the driven element of theapplication object and comprises said second engaging means, the drivenelement of the application object forming a part whose position isspatially determined and which determines the position of said coneapex.
 3. An eccentric gear according to claim 2, wherein the teeth ofthe third gear ring have a smaller axial length than the correspondingteeth in the fourth gear ring in order to enable the third gear ring tomove axially relative to the casing part without the gear rings losingtheir meshing with each other and without the cone apex changing itsposition relative to the application object.
 4. An eccentric gearaccording to claim 2, wherein the first and second gear rings have aconical basic shape, with small ends and large ends and engage into eachother with the small ends pointing in the same direction, and furtherincluding a fixed shoulder within the casing, serving as an intermediatewall, against which an end of a compression spring may abut, and whoseopposite end may abut against the driven element of the applicationobject, so that the spring in a compressed state biases the conicalfirst and second gear rings into engagement with each other.
 5. Aneccentric gear according to claim 4, wherein the first outer gear ringis provided on the inside of a frame-forming ring which has means toconnect the ring to the application object and to a motor, with anoutput shaft that is centrically mounted in bearings for driving aneccentric body that forms a driving element for the eccentric gear. 6.An eccentric gear according to claim 1, wherein the elongated body ismounted in bearings by a first, eccentrically placed bearing in theregion of said second gear ring and by a second centrically placedbearing at the opposite end of the elongated body, which second bearingis kept in place by means of a stationary holder that determines theposition for said cone apex, and that the elongated body in the regionof the second bearing has an external, fifth gear ring, which forms saidfirst engaging means and has the purpose of being led into engagementwith a complementary second engaging means, in the form of a gear wheel,that is connected with the rotary element of the application object. 7.An eccentric gear according to claim 1, wherein an outer tap is includedin the elongated body, which tap has an external thread which is inengagement with an internal thread in a hole in a fixed holder and whichtap, when rotating, may be set in axial motion in both directions bysaid thread engagement, in order to influence an arm or a link.